An oil-based ball point pen that is conventionally known, for the purpose of preventing the movement of the ink, uses high-viscosity ink. Further, the oil-based ball point pen makes the ink-accommodation tube thin to thereby cause an increase in the capillary attraction force and thereby prevent the movement of the ink. However, as a result of this, there are the drawbacks such as heavy writing sensation, ink blobbing, uneven drawn lines, or low writing density. Also, there is known a so-called "a sliver type water-based ball point pen", in which a low-viscosity ink is impregnated into a fibrous sliver and this ink is guided up to a ball-pen tip via an ink-guiding center core. However, this type of ball point pen has the following drawbacks. Namely, the consumption of the ink is not known. The flow rate of the ink decreases with the progress of the writing, with the result that density of drawn lines become low. And, because of the necessity of drawing out the ink from the sliver, it is necessary to make the viscosity of the ink 2 to 3 cps and make the surface tension of the ink low. It results from this that the ink is likely to be blurred on the paper surface. Also, there is known a so-called "collector-type" of ink direct-storing type water-based ball point pen (hereinafter called "a collector ball point pen") to which in order to eliminate the above-described respective drawbacks there is applied a mechanism that has hitherto been used in a fountain pen, wherein an ink tank having ink directly stored therein is disposed rearward; and the replacement of air during the writing is adjusted via the internal pressure by means of a collector having a large number of vane-like grooves. However, in the collector ball point pen, the flow rate of the ink is as high as that of the water-based ball point pen. In addition, it is necessary to make the amount of ink loaded greater than that of the oil-based ball point pen. Therefore, in the collector ball point pen, it is practiced to make the diameter of the ink tank large and to store ink generally in volume of about 2 to 3 cc in the ink tank.
In the conventional collector ball point pen, when the fluctuation in the atmospheric pressure of the outside air occurs, the ink is moved into the collector to thereby adjust the internal pressure of the ball point pen. The ink is thereby prevented from leaking out from a tip of the pen. In the conventional collector ball point pen, in order to prevent the ink from being volatilized, it is generally practiced to provide a cap for hermetically closing the interior of the pen, by providing an undercut over the entire circumference of the inner surface of the cap so as to simultaneously seal the air hole and the pen tip and airtightly closing them. However, in this conventional collector ball point pen, there exists a drawback of a spilling over phenomenon that occurs due to so-called "pumping phenomenon". Namely, owing to putting on/off the cap, the internal pressure thereof changes and, as a result, the ink gradually gets more and more filled into the collector. And at last the amount of ink gets more than the limit up to which the collector can store the ink therein and the ink spills over from the air hole.
In order to eliminate the above-described drawbacks, there has hitherto been made a proposal in which a cap has the following cap mechanism. Namely, a spring 22 and a movable inner cap such as those illustrated in FIG. 1 are combined together. And it is arranged to hermetically seal the point assembly of the pen body by means of a seal surface 23 of the inner cap 21. In this cap mechanism, from the instant in which the seal surface 23 has been able to close the point assembly, even when any further axial stroke of the cap 12 occurs, no change occurs in the internal volume of the inner cap 21. In this cap mechanism, therefore, no change resultantly occurs in the internal pressure thereof and therefore no pumping phenomenon occurs. Also, in FIG. 1, a reference numeral 20 denotes an integrated barrel. Namely, FIG. 1 illustrates a disposable type ball point pen wherein a front barrel and a rear barrel and an ink tank are integrally formed together. However, this proposal had such drawbacks that the structure was complex and high in cost and also that the outside diameter of the cap 12 became large. It is to be noted that other portions in FIG. 1 than those described above are common to the portions shown in an embodiment as later described. And these portions will be described later.
Also, there is the drawback that the spilling over phenomenon occurs, as in the case of the preceding ball point pen examples as described, in the same mechanism when a decrease in pressure and an increase in pressure repeatedly occur as at the time of heating/cooling, within an airplane, under a high/low atmospheric pressure, at a high/low position in level, etc. In order to eliminate the above-described drawbacks, there have also been taken measures for solution to them, such as a measure to make further large the maximum amount of ink stored in the collector (to make large the diameter and the length thereof), a measure to make the ink tank small in size, etc. However, these measures are followed by such drawbacks that the size of the barrel of the ball point pen becomes large to cause degrading of outer appearance thereof, the content of ink becomes less with the result that the service life of the ball point pen becomes short to cause a deterioration of the cost performance, etc. Namely, even in the case of taking those measures, only products of a level having such drawbacks have hitherto been put to practical use.
The present invention has an object to provide mainly an improvement of a popular model of collector type water-based ball point pen. The present invention has satisfied, without obstructing performance of smooth writing during writing, a demand for reliably enhancing the following failure-preventing performance. The failure-preventing performance includes an ink leak-out preventing performance that, during transportation or at the time of putting on/off the cap, prevents the ink from leaking out due to the influence from an increase or decrease in the atmospheric pressure. The failure-preventing performance also includes a spilling over-preventing performance that prevents the spilling over of the ink in a case where the ball point pen has been kept displayed over a long period of time in a store, etc. By satisfying such demand, the present invention has an object to simultaneously settle subject matter such as eliminating such serious drawback as staining consumer's clothes, a demand for a collector type of ball point pen, which tends to become large in diameter, to have a slim outer appearance, and the cost performance that by replacing only the ink tank with another one it becomes possible to perform further writing, as well as to satisfy the writing performance as the conventional collector type ball point pen has.